A conventional tuning fork type angular velocity sensor has a detecting part comprising detector plates 13 and 14 and a driving part comprising driver plates 11 and 12. As shown in FIG. 19, detector plates 13 and 14 are located at the top of the driver plates 11 and 12, respectively. Each detector plate 13 and 14 is joined orthogonally to a respective driver plate 13 and 14. When an angular velocity is applied to the angular velocity sensor and while keeping the driving part in continuous tuning fork vibration, the angular velocity is detected by the output of the detector plates 13 and 14, which vibrate in opposite directions to each other corresponding to the applied angular velocity.
In an angular velocity sensor in accordance with the prior art, a tightly sealed space is formed by a lid 2, which is made of resin. Lid 2 is attached at an aperture of a case 1, also made of resin, of which one end is open, as shown in FIG. 18.
Inside the tightly sealed space, a circuit board 3 and a metallic weight plate 4 are contained. Supporting pins 5 are attached at four corners inside the case 1, and weight plate 4 and circuit board 3 are elastically supported and fixed by the supporting pins 5. Dampers 6 made of rubber are attached at the four corners of weight plate 4 for the elastic support. Supporting legs 7 made of resin are put between damper 6 and circuit board 3. Supporting pins 5 are compressed at the tips toward the circuit board 3 side after penetrating dampers 6, supporting legs 7 and circuit board 3. Thus, circuit board 3 and weight plate 4 are elastically supported and fixed. A metallic supporting pin 8 is inserted and fixed vertically to weight plate 4, on the circuit board 3 side, as shown in FIG. 19. One end of a metallic supporting pin 9, laid parallel to weight plate 4, is inserted and fixed to supporting pin 8. The diameter of supporting pin 9 is about one fifth of the diameter of supporting pin 8. Furthermore supporting pin 9 is made of metallic material having elasticity, such as a piano wire, wherein the other end of supporting pin 9 is fixed to a metal plate 10 by soldering.
One end of each of metallic driver plates 11 and 12, which are sandwiching supporting pins 8 and 9 therebetween, is fixed to each side of metal plate 10. Plate-shaped piezoelectric elements 11a and 12a are fixed on the surfaces of metallic driver plates 11 and 12, respectively. In this way, the tuning fork type driving part is formed. The other ends of driver plates 11 and 12 are twisted orthogonally relative to piezoelectric elements 11a and 12a to form detector plates 13 and 14. Other plate-shaped piezoelectric elements 13a and 14a are fixed on detector plates 13 and 14, as shown in FIG. 19. In this way, the detecting part is formed. The angular velocity sensor is composed of the driving part and the detecting part.
There is a problem with the conventional angular velocity sensor however. Namely, the conventional sensor has no ability to detect information about the occurrence of a malfunction of the components, nor the ability to send such information, judged to be a malfunction of the components, to the outside (e.g., such that an operator can be notified of the malfunction).
The present invention provides a sensor that allows detection from outside the sensor of a malfunction in the sensor, resulting from partial damage to the sensor, that prevents the sensor from performing accurate angular velocity detection. Accordingly, the present invention provides a highly reliable angular velocity sensor.